An inkjet printing system, as one embodiment of a fluid ejection system, may include a printhead assembly, an ink supply which supplies liquid ink to the printhead assembly, and a controller which controls the printhead assembly. The printhead assembly, as one embodiment of a fluid ejection device, ejects ink drops through a plurality of orifices or nozzles and toward a print medium, such as a sheet of paper, so as to print onto the print medium. Typically, the orifices are arranged in one or more arrays such that properly sequenced ejection of ink from the orifices causes characters or other images to be printed upon the print medium as the printhead assembly and the print medium are moved relative to each other.
Typically, the printhead assembly ejects the ink drops through the nozzles by rapidly heating a small volume of ink located in vaporization chambers with small electric heaters, such as thin film resistors, often referred to as firing resistors. Heating the ink causes the ink to vaporize and be ejected from the nozzles. Typically, for one dot of ink, a remote printhead assembly controller typically located as part of the processing electronics of a printer, controls activation of an electrical current from a power supply external to the printhead assembly. The electrical current is passed through a selected firing resistor to heat the ink in a corresponding selected vaporization chamber. The combination of a nozzle, a vaporization chamber, and a firing resistor is herein referred to as a drop generator.
One method of controlling the application of the electrical current through the selected firing resistor is to couple a switching device, such as a field effect transistor (FET), to each firing resistor. In one printhead arrangement, the firing resistors are grouped together in primitives, with a single power lead providing power to the source or drain of each FET for each firing resistor in a primitive. Each FET in a primitive has a separately energizable address lead coupled to its gate, with each address lead coupled to its gate, with each address lead shared by multiple primitives. In a typical printing operation, the address leads are controlled so that only a single firing resistor in a primitive is activated at a given time.
In one arrangement, the address lead coupled to the gate of each FET is controlled by a combination of nozzle data, nozzle addresses, and a fire pulse. The nozzle data is typically provided by the controller of the printer and represents the actual data to be printed. The fire pulse controls the timing of the activation of the electrical current through the selected firing resistor. Typical conventional inkjet printing systems employ the controller to control the timing related to the fire pulse. The nozzle address is cycled through all nozzle addresses to control the nozzle firing order so that all nozzles can be fired, but only a single nozzle in a primitive is fired at a given time.
While such arrangements are effective in controlling nozzle firing, connections between the printhead assembly and remote elements and between elements on the printhead assembly itself can become complex, especially as the number of nozzles and the area of the printhead assembly increase. An example of one such system is a wide-array inkjet printing system. Printing systems, particularly wide-array inkjet printing systems, would benefit from a simplified nozzle firing activation scheme.